Many electronics systems have low-lying obstructions such as board components or socket attach mechanisms that limit the size of heat sinks, thus limiting thermal performance. Thickening the base enables the heat sink to be raised above the obstructions with fins placed over the top of the base. However, the thickened base increases conduction resistance and reduces temperatures for the fins furthest from the source, both of which degrade heat sink performance.
A common heat sink implementation uses a high conductivity material such as copper for constructing the base to minimize conduction resistance and maximize heat spreading. However, the added mass of a large copper base imposes a higher load on a heat sink attachment mechanism and increase the probability of failures due to shock and vibration. In addition, even a copper base may be insufficient to create suitable thermal performance.
Other heat sink implementations use heat pipes to aid in heat spreading. Unfortunately, the large bend radius of heat pipes can limit the geometry of the heat sink base and the solder or adhesive attaching the heat pipes to the base can significantly increase thermal resistance.